The fixation or stabilization of the upper and lower dental occlusal arches to one another is known as intermaxillary fixation (IMF), also known as maxillo-mandibular fixation (MMF). IMF has historically been a necessity in the treatment of all reconstructive jaw procedures.
The earliest methods for providing IMF consisted of wiring techniques, in which metallic wires were placed around one or more (adjacent) teeth at their base(s) and were then twisted down to the teeth in a secure manner. When a wire is passed around a tooth (or teeth) at the base in such a way, it may be termed a circumdental wire ligature (CWL). Multiple CWL's can be placed along the span of the dental arch in a series, or the wire may also be fashioned such that a single continuous strand incorporates multiple teeth along the arch securely. In whatever manner this is accomplished, both upper and lower arches are so treated, and subsequently the jaws are then secured to one another with wire loops or elastics incorporating single or multiple CWLs on the opposing jaws, thus accomplishing IMF.
Arch bars (or arch wires) are known to those of skill in the art. Arch bars involve the use of a linear metal bar or wire that may be applied and secured to the dental arch form. Arch bars typically have a plurality of hooks/tabs facing in a single direction. The arch bars and their corresponding hooks are placed in opposing directions for the upper and lower jaws so that wire loops or elastics could securely affix the jaws together. Arch bars typically impart stability to one or both the maxillary or mandibular arch. The relatively rigid bar spanning along the dental arch provides stability along the upper border of either jaw even when a fracture is present between teeth. A plurality of hooks allows placement of elastics or wire loops between the jaws at varying angles to potentially affect varying, advantageous tension vectors. The two common methods of securing all arch bars are (1) via CWL placed around the teeth in routine fashion but incorporating the arch bar; and (2) via orthodontic adhesives of a variety of types
However, both methods suffer drawbacks. For example, the most common means to secure arch bars is via multiple circumdental wire ligatures. This is a time-consuming process, associated with significant discomfort and potential for dental injury. The wire ligatures themselves are uncomfortable and often must be adjusted/tightened by the treating physician. Removal of arch bars applied using CWL's, is equally uncomfortable, and there is further potential for dental injury. In addition, in some CWL's require removal under operative anesthesia, with the associated risks of anesthesia.
While orthodontic adhesives are known, they too have disadvantages, in large part due to the conditions under which IMF is performed. For example, IMF is often performed by a surgical specialist, who is unfamiliar with the techniques and procedures used by orthodontists and dentists in the area of dental adhesives. The procedures are also, many times, conducted in a trauma setting where damage and blood loss limit the ability to work with such adhesives—which require a relatively clean, dry field for efficacy.
Adhesive techniques and circumdental wiring techniques both require adequate dentition. Both techniques may be severely limited or even precluded in conditions for dental injury, loss, or preexisting poor dental health.
Another method of IMF utilizes individual screws, placed in the bone between tooth roots, with a portion of the screw projecting external to the gingival or mucosa. Two or more IMF screws are typically placed into each of the upper and lower jaws. A wire loop is then either wrapped around the exposed portion of two opposing screws, or through a hole that is drilled through each of the two opposing screw heads, to provide IMF.
The advantages of IMF screw fixation include speed of placement and comfort. The screws rarely require adjustment, are well-tolerated, and are easily removed. However, IMF screws do not provide stability along the dental arch as does an arch bar. Ideally, IMF is used not only for immobilization, but also for accurate restoration of occlusion. For fractures occurring between teeth, IMF screws do not provide upper border stabilization nor flexible technical application methods to optimize occlusion. Finally, it is difficult (if not impossible) to apply elastics between IMF screws. Elastic IMF is safer than wiring the jaws together, and is often preferred for specific fracture types in which the surgeon would prefer the patient to have guided mobility of the jaws rather than relative immobilization.
Most of the technologies proposed for IMF technologies to date have been developed by orthodontists and oral surgeons. These dental specialists have been understandably inclined to consider only methods which involve fixation to teeth, a concept that has been historically accepted and perpetuated since the early 1900's. The most significant developments in reconstructive jaw surgery in the modern era have focused largely on methods for internal fixation (plating), rather than IMF. However, internal fixation is not a replacement for IMF, nor does is preclude the need for IMF in most cases, which is still a mandatory procedure for reconstruction of the dental arches.
Despite early developments in dental arch fixation technology, and advanced developments in other dental areas, there is currently no way to anchor existing arch bars to bone or other prosthetic dental devices using existing technologies.